Victories for the 501(c)4 non-profit lobbying organization, founded by conservative lobbyist Grover Norquist in 1985, would undoubtedly complicate efforts to reach a deal to avert the so-called "fiscal cliff" because the group "opposes all tax increases as a matter of principle." ATR's central tenet — the Taxpayer Protection Pledge, which requires lawmakers to "solemnly bind themselves to oppose any and all tax increases," enjoys the backing most Republicans in Congress and all but one of this year's GOP presidential candidates. But there have been some notable dissenters.

Norquist's influential group has reported spending a total $3.9 million on House and Senate races, almost all in the last two weeks. In the last 24 hours alone, ATR clocked $1.97 million in independent expenditures in reports to the the Federal Election Commission. All were for negative television ads, like the one seen above, against Democrats in six House races, three of them involving Republican freshmen:

$185,000 to oppose the reelection of rookie Democratic Rep. Mark Critz in Pennsylvania's 12th Congressional District, another tossup, according to the Cook Political Report. ATR's latest expenditures are in addition to $495,000 the group dumped into the race earlier this month.

$374,000 to boost freshman Rep. Scott Tipton, R-Colo., against state Rep. Sal Pace in Colorado's 3rd district. Before this weekend, the race had seen less than $90,000 in total outside spending, but Tipton has received strong support from GOP insiders. While Cook still rates Tipton the favorite to win a second term, he has moved the contest from "likely" to "lean" Republican.

$519,000 in Ohio's 6th Congressional District, where former Democratic Rep. Charlie Wilson is trying to snatch the seat back from the freshman Republican who unseated him two years ago, Rep. Bill Johnson. While Cook gives Republicans the edge to keep this seat, he cautions that polls show the race is "quite tight."